The present invention is a method and apparatus for treating the bore of a hydrocarbon producing well, and more specifically a method and apparatus for cleaning a wellbore and stimulating hydrocarbon production from surrounding formations by removing particles therefrom by subjecting the particles to vibratory waves produced by two or more vibratory wave generators.
An ongoing problem with hydrocarbon producing wells is maintaining flow therefrom. Over time, the interior surface of the wellbore and the pores and fractures in the producing formations tend to become clogged with particles, contaminants, scale, earthen debris and the like. Also, a hydrocarbon well typically must be serviced during its production life, which frequently requires circulation of mud in the well. An undesirable side effect of such circulation is the formation of a residual mudcake adhered to the interior surface of the wellbore that can further inhibit hydrocarbon production from the formation. The present invention solves these clogging problems by employing a plurality of vibratory wave generators to produce vibratory waves which loosen the contaminant particles from the surfaces of the formation fractures and wellbore where they can be lifted out of the well by a circulating fluid during treatment or by hydrocarbons during production.
The present invention discloses a process and apparatus for treating a wellbore, comprising subjecting a substantially same portion of the wellbore to vibratory waves produced by a plurality of vibratory wave generators. The vibratory waves may have about the same frequency or a plurality of frequencies, and the frequencies may partially overlap, not overlap, or be modulated across a range. Additionally, the frequencies may be modulated in the oval, hoop, and flexural modes. The vibratory waves may be produced by firing the vibratory wave generators simultaneously or in sequence. Preferably, the vibratory waves are acoustically streamed in a viscous boundary layer near obstacles, outside a viscous boundary layer near obstacles, or in a free non-uniform sound field. In a preferred embodiment, a vibrating pipe and a piston pulser are used as vibratory wave generators. In another preferred embodiment, a vibrating pipe, piston pulser, and a valve are used as vibratory wave generators. In another preferred embodiment, the thickness and change of thickness of a mudcake on the interior surface of a wellbore is measured to evaluate the effectiveness of the wellbore treatment. The speed of sound in the wellbore fluid is calculated. An ultrasonic signal is transmitted from a transducer, and the time of flight for an echo reflected from the boundary of the wellbore fluid and the mudcake back to the transducer is measured. At a later time in the same waveform, an echo reflected from the boundary of the mud cake and the interior surface of the wellbore back to the transducer arrives. The time of flight for this second echo is also measured. The thickness of the mudcake is calculated according to the equation L=(T2xe2x88x92T1)*c/2, where L is the thickness of the mudcake, c is the speed of sound in the wellbore fluid, T1 is the time of flight for an echo reflected from the boundary of the wellbore fluid and the mudcake, and T2 is time of flight for an echo reflected from the boundary of the mudcake and the interior surface of the wellbore. The change in thickness of the mudcake between a second point in time after a first point in time is calculated according to the equation xcex94L=0.5*(T1a*caxe2x88x92T1b*cb), where xcex94L is the change in thickness of the mudcake, ca is the speed of sound in a wellbore fluid at the second point in time, cb is the speed of sound in the wellbore fluid at the first point in time, T1a is the time of flight for an echo reflected from the boundary of the wellbore fluid and the mudcake measured at the second point in time, and T1b is the time of flight for an echo reflected from the boundary of the wellbore fluid and the mudcake measured at the first point in time.